Spin relaxation of indirect excitons in asymmetric coupled quantum wells

Density and spin dynamics of indirect excitons in asymmetric GaAs/AlGaAs coupled quantum wells is studied by time-resolved photoluminescence. Under electric bias applied in the growth direction the lifetime of indirect excitons formed by an electron in a wide and hole in a narrow quantum well reaches 12 ns, while the circular polarisation lifetime is about 5 ns. The structure is suited for further studies of dark indirect excitons by time-resolved pump-probe spectroscopy.